Hardware Reference
In-Depth Information
FIGURE 3.23 Penalties for all possible combinations of whether the branch is in the
buffer and what it actually does, assuming we store only taken branches in the buffer .
There is no branch penalty if everything is correctly predicted and the branch is found in the
target buffer. If the branch is not correctly predicted, the penalty is equal to one clock cycle to
update the buffer with the correct information (during which an instruction cannot be fetched)
and one clock cycle, if needed, to restart fetching the next correct instruction for the branch. If
the branch is not found and taken, a two-cycle penalty is encountered, during which time the
buffer is updated.
 
Search WWH ::




Custom Search